The role of the striate cortex in the control of visually guided eye movements in the rhesus monkey has been studied by analyzing the visually guided saccades and smooth pursuit eye movements in animals with unilateral lesions of striate cortex. Lesions were made surgically, under direct vision, and the animals studied for up to a year and a half after the lesions. The animals can make normal saccadic eye movements to stationary targets in the blind field, and they can accurately locate the position of targets moving in the hemianopic field. However, they cannot modify their behavior to adjust for the velocity of the moving target. Thus they do not change the amplitude of a saccade to compensate for the ongoing movement of the target, nor do they adjust the strategy of their reaction times according to the direction in which the target is moving. Thus a striate cortex lesion can make an animal "velocity blind" in a manner analogous to a retinal lesion's making a human color blind. These data indicate that the striate cortex contributes velocity information to the oculomotor system, and that in the absence of striate input the oculomotr system functions mechanically quite well, but just behaves as if the target were not moving.